Science

How much of a threat is the Brazil variant of coronavirus to the UK?

Hospitals are at full capacity in Araraquara in Sao Paulo, Brazil

Igor Do Vale/ZUMA Wire/Shutterst

Health officials in the UK are trying to trace someone who tested positive for the P.1 coronavirus variant from Brazil after sending in a home test kit without contact details. So far, only six cases of P.1 have been detected in the UK – three in Scotland and three in England – but the situation has led to fears that this variant could spread more widely.

Existing vaccines should stop people getting severely ill and dying if they do get infected by the P.1 variant. However, because many people remain unvaccinated, plans to ease lockdown restrictions would have to be rethought if this variant causes a resurgence in case numbers. Plus, any variant that circulates widely will have more opportunities to evolve into a more dangerous form.

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The P.1 variant emerged in Brazil in November, and has now been detected in at least 25 countries. However, the number of cases detected outside Brazil remains low, and local transmission has been reported only in Sweden, Belgium, Mexico and Colombia.

Our knowledge of P.1 is very limited because it can only be detected by sequencing, and most countries do little sequencing. However, the big worry about the P.1 variant and the similar B.1.351 variant from South Africa is that they have mutations that enable them to partly evade antibodies people have from previous infections or from vaccinations. They also appear to be able to spread even in populations with a high proportion of herd immunity.

The P.1 variant may be to blame for a major second wave of infections in the city of Manaus, Brazil, despite up to three-quarters of the population getting infected in the first wave early in 2020.

Read more: Inside the race to tweak covid-19 vaccines and stay ahead of mutations

Thankfully, these variants cannot completely evade immune protection. Our bodies produce both antibodies that prevent the virus infecting cells in the first place, and T-cells that destroy infected cells to stop the virus making more copies of itself.

To prevent infection, antibodies have to bind to key sites on the spike protein that protrudes from the virus. Mutations in these key sites can reduce the effectiveness of these antibodies.

T-cells, by contrast, are effective as long as they recognise any part of the spike protein, so it is much harder for a virus to mutate to evade the T-cell response. “There is no way these variants are escaping T-cell immunity,” Shane Crotty at the La Jolla Institute for Immunology in California told New Scientist in January.

Trials of the Johnson & Johnson vaccine found it was slightly less effective at preventing symptomatic covid-19 in South America where P.1 is more common than in the US. However, the difference was small – 66 instead of 72 per cent – and crucially it was still 100 per cent effective at preventing hospitalisations and deaths. These findings are reassuring, as they mean that variants like P.1 will not wipe out all the benefits of vaccination even if they do start spreading widely.

Read more: What do the new coronavirus variants mean for a return to normality?

That said, there are still two big worries. The first is that even in the UK there are still many vulnerable people who have not been vaccinated. If a variant such as P.1 starts spreading widely and reaches these vulnerable people, hospital admissions and deaths could soar again, threatening the plan for easing of lockdown restrictions.

The second worry is that the more widely variants such as P.1 circulate, the more opportunity they have to evolve further. For instance, the fast-spreading B.1.1.7 variant that was first discovered in Kent, and was partly to blame for the recent resurgence of cases in the UK appears to have acquired the same E484K mutation that helps P.1 dodge antibodies.

“It is possible that as more and more people get vaccinated, and the selective pressures intensify on the virus, that we will see other mutations,” says Astrid Iversen at the University of Oxford. However, there is a limit to what evolution can achieve.

It is likely that many mutations have “fitness costs” as well as “fitness benefits”, Iversen says. This might explain why variants with the E484K mutation appeared early in 2020 but died out rather than spreading widely.

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